Commutator



juh; 25, 939. M. R. HANNA 2,3167479 COMMUTATOR Filed Janl 2l, 1938 Figi COM/3EE55ED V////////// Z9 s ii 33; M f6 ff! i lhventoY-z M m R. Hanna,

Patented July 25, 17939 ilNiTED STATES FATENT OFFICE ooMMUTA'roR Application January 21, 1938, Serial No. 186,097

1l Claims.

My invention relates to commutat'ors for dynamo-electric machines.

In commutator constructions employing an assembly of commutator bars, it has been found desirable to secure together the commutat'or bar assembly by clamping rings provided with wedge flanges arranged to engage complementary wedge surfaces formed in the ends of the commutator bars. Commutators .of large diameter usually are arranged with the outer wedge surface of the clamping ring wedge flange out' of engagement with the outer wedge surface of the commutator bar grooves, and the bars are secured together by the arching pressure between adjacent bars on the mica insulation between these adjacent bars. This construction, however, often is not practical for small diameter cornmutators, as it is difficult to obtain the correct arching pressure, and yet produce a regular cylindrical commutator bar assembly which does,I not bulge or become loose with expansion and contraction due to heating and cooling of the commutator under different operating conditions. In order to overcome this difficulty, the outer wedge surface of the clamping ring used on small diameter commutators usually is made so that it engages the outer Wedge surface of the commutator bar groove adjacent the outer end of the bars, and does not engage the portion of the commutator bar groove outer wedge surface adjacent the apex or bottom of the wedge groove. The inner wedge surface of the clamping ring wedge flange also usually engages the inner or smaller diameter commutator bar wedge groove surface. Commutators utilizing this latter construction are secured in assembled relation by the wedging pressure between the two wedge surfaces of the clamping ring and the commutatcr bars. However, it has been found that there is a tendency for the outer ends of the commutator bars which form the wedge to bend outwardly under the wedging pressure, resulting in a loose commutator bar assembly which does not provide a truly cylindrical commutator surface. Furthermore, when the commutator expands and s contracts due to heating and cooling of the various parts of the commutator when in operation, there is a tendency for the clamping ring to pivot about the inner and outer contact points of the wedge, and thereby to spread apart the relatively narrow sections of the commutator bars adjacent the commutator bar wedge surfaces, as well as to wear these contact surfaces and produce a loose commutator assembly.

An object of my invention is to provide an improved commutator construction which will provide the desired clamping pressure in large or small commutators for retaining the bars in assembled relation under all operating conditions, without distortion of the commutator assembly.

Further objects and advantages of my invention will become apparent and my invention Will be better understood from the following description referring to the accompanying drawing, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming part of this specication.

In the drawing, Fig. l is a partial elevational side view of a rotatable member of a dynamoelectric machine having a cornmutator embodying my invention, Fig. 2 is a sectional elevational view of my improved commutator construction, and Fig. 3 is an enlarged fragmentary view of the outer end of the commutator indicating the relative arrangement' of the insulation between the commutator bars.

Referring to the drawing, I have shown in Fig. 1 a rotatable member I0 for a dynamo-electric machine mounted upon a shaft Il and provided with a commutator including an assembly of commutator bars l2. The commutator bars l2 are provided with risers I3 adapted to be connected to leads of a winding arranged on the rotatable member Il). In order to support the commutator bars in assembled relation, a supporting hub I6 is arranged with an axially extending cylindrical portion l5 arranged within and closely adjacent the inner axial edges I6 of the commutator bars l2. An annular wedge-shaped flange Il having an inner Wedge surface E3 is formed on the supporting hub and is arranged to bear against an inner wedge surface I9 of a wedge groove 2G formed in the inner end of each commutator bar YI 2, and an outer relatively narrow wedge shoulder surface 2i is arranged to engage an outer wedge surface 22 of the commutator bar wedge groove 2. This wedge shoulder 2| is formed axially of the wedge flange Il adjacent the axial center of the inner wedge surface I9 and provides an outward wedging pressure on the commutator bar outer wedge surface adjacent the center of pressure between the Wedge flange and the commutator bar inner wedge surface. Substantially all of the remainder of the outer surface of the wedge ange l1 is arranged out of engagement with the commutator bars I2, as the inner end and the outer portion of the outer wedge surface of the wedge flange l'l are undercut with respect to the wedge shoulder 2l. With this arrangement, the vertical components of the CII wedging forces between t'he wedge flange I1 and the commutator bars are substantially in line, and the moment arm between the two wedging forces on the inner and outer surfaces of the commutator bar wedge grooves 20 is substantially reduced. Sheets 23 and 24 of suitable insulating material, such as pressed mica, are arranged between the commutator bars I2 and the surfaces of the hub flange I1 and the cylindrical hub surface I5, respectively, in order to electrically insulate the commutator bars I2 from the supporting hub I4. The supporting hub I4 yis formed with a plurality of axially extending Ventilating openings '25 throughwhich air may :be circulated in order to coolnthecommutator, and a central hub section 26 is adapted'to besecured to the shaft II in order to properly mount the commutator thereon.

In order to retain the commutator bars in assembled relation, I provide a clamping ring 21 which is secured to the supporting hub I4 by a plurality of screws 28 threadedly engaging complementary threaded openings in the outer end of the cylindrical portion I of the supporting hub. The clamping ring 21 is formed with an annular wedge flange 29 having a conical section and arranged to fit within a wedge groove 3l! formed in the outer end of each of the commutator bars I2. The commutator bar wedge groove 30 is provided with an out'er wedge surface 3I and is tapered inwardly from the outer edge of the commutator bar toward the inner end or apex 32 of the wedge groove and an inner wedge surface 33 extending axially of the commutator substantially less than the outer wedge surface 3l and being tapered radially outwardly from the outer end 34 of the wedge surface 33 toward the apex 32 of the wedge groove 30. A sheet 35 of suitable insulating material, such as pressed mica, is arranged between the clamping ring 21 and the commutator bars I2 in order to electrically insulate the commutator bars from the clamping ring. The clamping ring wedge flange 29 is provided with an inner wedge surface 36 tapered radially .outwardly toward the apex or end 31 of the flange 29 and is arranged to engage the inner wedge surface 33 of the commutator bar wedge grooves 30 in order to provide an inward clamping pressure thereon axially and radially of the commutator bars I2. The outer surface of the clamping ring wedge flange 29 is provided with an outer relatively narrow wedge shoulder 38 tapered radially inwardly toward the apex 31 of the wedge flange, and is arranged axially of the clamping ring adjacent the axial center of the inner wedge surface 36 of the wedge flange 29. This wedge shoulder 38 is arranged to engage the outer wedge surface 3l of the commutator bar wedge grooves 30 to provide an outward wedging pressure on the outer commutator bar wedge surface adjacent the center of pressure between the wedge flange and the commutator bar inner wedge surfaces. Substantially all of the remainder of the outer surface of the wedge flange 29 is arranged out of engagement with the commutator bars I2, as the inner end 39 and the outer portion'40 of the clamping ring wedge flange 29 are undercut to a smaller diameter than the outer wedge surface of the wedge shoulder 38. With this arrangement, the vertical components of the wedge forces between the clamping ring and the commutator bars are substantially in line, and the resulting moment arm between these two wedge forces on the inner and outer wedge surfaces of the commutator bar wedge grooves 39 is substantially reduced, thereby allevare substantially eliminating the tendency for the clamping ring to pivot about the Contact points at the edges of the inner and outer wedge surfaces as the commutator expands and contracts due to variations in temperature under different operating conditions. This construction provides substantially a universal joint between the inner and outer wedge surfaces due to the relatively narrowwedge shoulder 38 and the substantial axial alignment of the center of pressure on the inner and outer wedge surfaces, 'so that any tendency for the clamping ring to pivot about the contact surfaces of the clamping ring wedge and the commutator bar wedge g'roves does not set up any excessive forces tending to spread apart the inner and outer portions all and 42 of the commutator bar on both sides of the commutator bar wedge groove 3B. Furthermore, the clamping ring wedge shoulder 38 is arranged adjacent the apex 31 of the clamping ring wedge 29, and therefore, engages the outer wedge surface 3| of the commutator bar wedge grooves 30 adjacent a section of the portion 42 of greater radial width than if the pressure were applied nearer the outer radial edge of the commutator bars I2. This construction also reduces the moment arm of the outward wedging pressure, as this outward pressure is applied to the outer wedge surface 3| of the wedge groove 30 of the commutator bars nearer the apex 32 of the commutator bar wedge groove 39, so that the tendency for the reduced portion 42 of the commutator bar to bend outwardly under the wedging pressure also is reduced substantially.

In order to utilize the above-mentioned arching pressure between the commutator bars for securely maintaining the bars in assembled relation, and to insulate electrically the commutator bars from each other, I provide a sheet of suitable insulating material 43, such as pressed mica of about 45 mils thickness, between adjacent commutator bars. As shown in Fig. 3, each alternate sheet 44 of the insulating material 43 is made of uniform thickness, while between the outer end portions 42 and 45 at both ends of the commutator bars extending over the outer wedge surfaces 3| and 22, respectively, the alternate insulating sheets intermediate those of uniform thickness are made of about .8 mil greater thickness. The intermediate alternate sheets of insulating material of greater end thickness comprise two groups 46 and 41 and sheets of these groups are alternately arranged between the sheets of uniform thickness. One group 46 extends from the outer ends of the bars to the inner end or apex of the wedge grooves and the other group 41 extends from the outer ends of the bars to about half the length from the outer ends of the bars to the apex of the grooves, as indicated by the dotted lines 48 and 49, and 59 and 5I, respectively. This increased thicknes of insulation between the outer ends of the commutator bars also can be made of a tapered gradually increasing thickness from lines 48 and 49 adjacent the apexes of the Wedge groove 30 and 20, respectively, and added to each sheet or strip of insulation between commutator bars. This provides a greater arching pressure between the outer ends of the commutator bars I2, as the insulation between this portion of the bars is more highly compressed than between the remainder of the bars, since the sides of the commutator bars are substantially straight and parallel. This assists in preventing distortion of the commutator assembly and in preventing bendingv of the portions of reduced radial dimension 42 of the commutator bars. This construction provides a commutator bar assembly which utilizes both the arching pressure between adjacent commutator bars and the v vedging pressure between inner and outer wedge surfaces for maintaining the commutator bars in assembled relation, and provides an `arrangement' which facilitates expansion and contraction of the commutator without producing excessive bending stresses on the parts of the commutator bars of reduced section, and thereby prevents distortion of the commutator and maintains a rigid assembly.

While I have illustrated and described a particular embodiment of my invention, modifications thereof will occur to those skilled in the art. I desire .it to be understoody therefore, that my invention is not to be limited to the particular arrangement disclosed, and I intend in the appended claims to cover all modifications which do not depart from the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

l. A commutator including a plurality of corn.- mutator bars, each of said commutator bars having a wedge groove formed with an inner and outer wedge surface in an end thereof, and means including a clamping ange for securing said commutator bars in assembled relation, said clamping flange having a tapered inner wedge surface arranged to engage said inner commutator bar groove wedge surface and an outer relatively narrow tapered wedge shoulder arranged to engage said outer commutator bar groove wedge surface adjacent the center of pressure between said inner wedge surfaces.

2. A commutator including a plurality of corn- Inutator bars, each of said commutator bars having a wedge groove adjacent each end thereof formed with an inner and outer wedge surface, a supporting hub arranged to support said commutator bars, means including wedge iianges having inner and outer wedge surfaces arranged to engage said commutator bar wedge surfaces for securing said commutator bars in position on said supporting hub, and insulation arranged between adjacent commutator bars having a greater thickness between adjacent ends of said commutator bars adjacent the outer wedge surfaces than between the remainder of said bars and extending from the outer ends of said commutator bars to adjacent the inner ends of said wedge grooves.

3. A commutator including a plurality of commutator bars, each of said commutator bars having a wedge groove formed with an inner and cuter wedge surface in an end thereof, a supporting hub arranged to support said commutator bars, and a clamping ring arranged tosecure said commutator bars in position on said supporting hub, said clamping ring having a tapered inner wedge surface arranged to engage said inner commutator bar groove wedge surface and an outer narrow tapered wedge shoulder arranged to engage said outer commutator gar groove wedge surface adjacent the center of pressure between said inner wedge surfaces.

4. A commutator including a plurality of commutator bars, each of said commutator bars having a wedge groove formed with an inner and outer wedge surface in an end thereof, a supporting hub arranged to support said commutator bars and provided with an annular flange arranged to align said commutator bars axially and radially thereof, a clamping ring arranged to secure said commutator bars in position on said supporting hub, said clamping ring having an inner tapered wedge surface arranged to engage said inner commutator bar wedge surface and an outer tapered wedge surface arranged to engage said outer commutator bar wedge surface to provide a wedging pressure thereon adjacent the center of pressure between said inner wedge surfaces and arranged out of engagement therewith over substantially all of the remainder thereof, and means for insulating said commutator bars from each other and from said supporting hub said clamping ring.

5. A commutator including a plurality of commutator bars, each of said commutator bars having a wedge groove formed with an inner and outer wedge surface in an end thereof, a supp-rting hub arranged to support said commutator provided with an annular ange arranged to align said commutator bars axially and radially thereof, a clamping ring arranged to sesaid commutator bars in position on said supporting hub, said clamping ring having an inner tapered wedge surface arranged to engage said inner commutator bar wedge surface and an outer reis-tively narrow tapered wedge shoulder arranged to engage said outer commutator bar wedge surface to provide a wedging pressure thereon adjacent the center of pressure between said inner wedge surfaces, and means for insulating said commutator bars from each other and from said supporting hub and said clamping ring.

6. A commutator including a plurality of comrnr-.tator bars, each of said commutator bars having a wedge groove formed with an inner and outer wedge surface in an end thereof, said inner wedge surface of said commutator bar groove extending axialiy of said commutator substantially liess than said outer wedge surface, a supporting hub arranged to support said commutator bars, a clamping wedge flange arranged to secure said commutator bars in position on said supporting hub and arranged to engage said inner commutator bar wedge surface to provide an outward wedging pressure on said outer commutator bar wedge surface adjacent the center of pressure between said wedge flange and said commutator bar inner wedge surfaces, and insulation between adjacent commutator bars having a relatively greater thickness between the ends of said commutator bars adjacent the outer wedge surface to the inner end of the wedge grooves than between the remainder of said bars.

7. A commutator including a plurality of cornmutator bars, each of said commutator bars having a wedge groove formed with an inner and outer wedge surface in an end thereof, said inner wedge surface of said commutator bar groove extending axially of said commutator substantially less than said outer wedge surface, a supporting hub arranged to support said commutator bars, a clamping ring having a wedge ange arranged to secure said commutator bars in position on said supporting hub, said wedge flange being arranged to engage said inner commutator bar wedge surface and arranged to provide an outward wedging pressure on said outer commutator bar wedge surface adjacent the center of pressure between said wedge flange and said cornmutator bar inner wedge surfaces, and insulation between adjacent commutator bars relatively more highly compressed between the adjacent sides of said bars at the outer ends thereof adjacent the outer wedge surface and extending substantially to the inner end of the wedge f grooves than'between the remainder of said bars.

8. A commutator including Va plurality of commutator bars, each of said commutator bars having a wedge groove formed with an inner and outer Wedge surface in an end thereof, a supporting hub arranged to support said commutator bars and provided with an annular flange arranged to align said commutator bars axially and radially thereof, a clamping ring arranged to secure said commutator bars in position on said supporting hub, said clamping ring having an inner tapered wedge surface arranged to engage said inner commutator bar wedge surface and an outer relatively narrow tapered wedge shoulder arranged to engage said outer gornmutator bar wedge surface to provide a Wedging pressure thereon adjacent the center of pressure between said inner wedge surfaces, means for insulating said commutator bars from said supporting hub and said clamping ring, and insulation between .adjacent commutator bars having a greater thickness between alternate adjacent ends of said commutator bars adjacent the outer wedge surfaces than between the remainder of said bars.

9. A commutator including a plurality of commutator bars, each of said commutator bars having a wedge groove formed with an inner and outer wedge surface in an end thereof, a supporting hub arranged to support said commutator bars, means including a wedge flange having an inner and an outer wedge surface arranged to engage said commutator bar wedge surfaces for securing said commutator bars in position on said supporting hub, insulation arranged between adjacent commutator bars having a greater thickness between alternate adjacent ends of said commutator bars adjacent the outer wedge surfaces than between the remainder of said bars, and said greater thickness of said insulation extending inwardly on alternate insulating elements of greater thickness from the outer ends of said commutator bars to adjacent the inner ends of said wedge grooves and to substantially half the distance from the outer ends of said bars to the inner ends of said wedgegrooves.

10. A commutator including a plurality of commutator bars, each of said commutator bars having a wedge groove formed with an inner and outer wedge surface in an end thereof, a supporting hub arranged to support said commutator bars, a clamping ring arranged to secure said commutator bars in position on said supporting hub, said clamping ring having an inner tapered wedge surface arranged to engage said inner commutator bar Wedge surface and an outer relatively narrow tapered wedge shoulder arranged to engage said outer commutator bar wedge surface, means for insulating said commutator bars from said supporting hub and said clamping ring, insulation between adjacent ccmmutator bars having a greater thickness between alternate adjacent ends of said commutator bars adjacent the outer wedge surfaces than between the remainder of said bars, and said greater thickness of insulation extending inwardly on alternate insulating elements of greater thickness from the outer ends of said commutator bars to adjacent the inner ends of said wedge grooves and to substantially half the distance from the outer ends of said kbars to the inner ends of said wedge grooves.

11. A commutator bar clamping ring provided with an annular clamping Wedge flange having an inner and outer surface and formed with an inner wedge surface tapered radially outwardly along said inner surface and an outer wedge shoulder formed Von said outer surface and tapered radially inwardly, said outer wedge shoulder being arranged adjacent the axial center of said inner wedge surface.

MAX R. HANNA. 

